NUMERICAL INVESTIGATION OF DIFFERENT SHAPED MICROCHANNEL HEAT SINKS EMBEDDED INSIDE SILICON SUBSTRATE OF HIGH-POWER DENSITY GAN POWER AMPLIFIERS

Ongoing efforts in miniaturization of electronics increase the significance of futuristic thermal management solutions. Especially for gallium nitride (GaN) based power amplifiers, it is crucial to spread heat generated by highly localized heat sources (hotspots) for enhanced operating performance and lifetime of GaN power amplifiers. To overcome thermal constraints of GaN power amplifiers, many active cooling solutions have been studied and further investigated in the literature. One of the most promising component level thermal management technologies is cooling via microchannel heat sinks, and in this study, number of microchannel shapes such as straight, wavy, hybrid straight-wavy, converging-diverging, and diverging-converging microchannels are investigated for benchmarking of cooling performances. Moreover, proposed single and double-layered microchannel designs are compared. Double-layered microchannels are also examined according to the direction of the microchannels. This allows us to determine which of the different flow directions - parallel and counter flow - most effectively reduce the hotspot temperature of GaN power amplifiers. While benchmarking different microchannel concepts, pressure drop values are also compared using friction factor. Results indicate that utilizing proposed hybrid concept and converging-diverging microchannels instead of conventional straight microchannels can reduce maximum gate finger temperatures, while keeping pressure drop throughout the channel at reliable levels. Outcomes of this study will be valuable for researchers aiming to utilize proper microchannel geometries to enhance thermal management of high-power dissipating GaN power amplifiers and similar chips reaching kW/cm(2) order of magnitude heat fluxes.